New so-called right-to-work legislation is on the way to becoming law in Michigan. It would no longer allow contracts that require union dues as a condition of employment. Michigan has one of the highest concentrations of unionized workers in the country. Many of them in a state's all-important car industry. The law is seen as a blow to the heart of the labor movement.

NPR's Sonari Glinton reports on what it could mean for automakers and the many companies that depend on them.

SONARI GLINTON, BYLINE: In the last few years, battles between organized labor and Republican-dominated statehouses raged across the Midwest. In Michigan, Republican Governor Rick Snyder avoided conflict, especially with one of the state's most powerful unions, the United Auto Workers, well, until yesterday.

GOVERNOR RICK SNYDER: We did the analysis and research just like we do on every other issue, make a decision and move on. And I've made a decision. I believe freedom of choice for workers is an important topic. Let's get it done now.

GLINTON: The general surprise, Snyder reversed his position on right-to-work legislation. And after years of saying it wasn't on his agenda, the governor said he'd sign bills that are racing their way through the lame duck session of Michigan's statehouse. The move has drawn the rage of labor in the state. Bob King, the head of the UAW, says if the governor wasn't itching for a fight before, he's got one now.

BOB KING: I think the governor was - received tremendous pressure from wealthy right-wingers in Michigan, and he succumbed to that pressure.

GLINTON: Actually, Labor may have started the fight by pushing for a ballot measure that would have enshrined collective bargaining in the state's constitution. That failed, and that emboldened Republican lawmakers.

KRISTIN DZICZEK: This is the opening shot in a long battle that will wage in Michigan. And this has energized and focused the entire union movement in Michigan on this.

GLINTON: Kristin Dziczek is with the Center for Automotive Research. She says auto manufacturers will often move to right-to-work states. That is, they may move to a right-to-work state where the laws are in place and stable.

DZICZEK: We have passed right to work, but there's going to be a big fight, and the (unintelligible) will be involved and there will be, you know, new legislators elected and, you know, we don't know for certain that right to work is the law of the land from here on forth.

GLINTON: Dziczek says this won't have a big impact on the Big Three. They all have plants in right-to-work states already. Here's the thing: All the Detroit automakers say they're either neutral or don't have a position on the law. Dale Belman is a professor of labor relations at Michigan State University. He says auto executives have not exactly been clamoring for right-to-work legislation, especially after winning so many labor concessions around the economic downturn.

DALE BELMAN: If you're headed in the right direction, the last thing you need is someone doing something that diverts your energy from that.

GLINTON: Belman says the legislation probably won't affect the Big Three, where union membership is very, very strong, at least not immediately. Where it could have an effect is with suppliers where the union membership is weaker and conflicts could erupt between workers.

BELMAN: And that might affect the ability of that parts supplier to supply parts on a regular basis, the way they're supposed to. I think the Big Three aren't just concerned with their immediate workforce. It's how it affects their whole supply chain.

GLINTON: Belman and other experts say after years of stabilizing and fixing their known problems, automakers are bracing for the unknown. Sonari Glinton, NPR News. Transcript provided by NPR, Copyright NPR.